THEORETICAL-ANALYSIS OF INTRAMOLECULAR DOUBLE-HYDROGEN TRANSFER IN BRIDGED-RING COMPOUNDS

Model calculations are reported on double-hydrogen and double-deuteriu m transfer rates in two bridged-ring molecules recently investigated b y Mackenzie et al. [Tetrahedron Letters, 33 (1992) 5629]. The calculat ions indicate that, contrary to an earlier interpretation, the two ato ms are transferred by asynchronous tunnelling, the observed activation energy being representative of the energy of the biradical intermedia te rather than the barrier height.